Pipes for delivering liquid or gaseous material are widely used in industry, and valves are essentially mounted on the pipes to control fluid flow. Such valves include various types, all of which function to control fluid flow or regulate the flow rate.
Since various types of valves exist, a suitable one is selected according to the use thereof. Important valves include ball valves, butterfly valves, gate valves, safety valves, diaphragm valves, needle valves, glove valves, angle valves and so on.
Among the various kinds of valves, the present invention relates to a valve, which includes a stem and a handle connected to the stem, and in which the handle and the stem operate in response to the rotation of the handle to adjust the flow rate or control fluid flow.
A conventional needle valve will be described briefly with reference to FIG. 1, which is a partial sectional view illustrating the structure of the needle valve.
The needle valve includes a stem 1, a body 2 and a handle 3. The stem 1 is connected at the bottom portion thereof to a disk to open or close a flow passage, the body 2 forms the basic exterior of the valve, the stem 1 protrudes from the top portion of the body 2, and the handle 3 is connected to the stem. A nut 4 is fastened to the top portion of the body 2 to press the same, thereby preventing leaks. Since the nut is constantly fixed, when the handle is rotated, the handle and the stem move up and down together.
However, since the needle valve does not have a safety device that can restrict the operation of the handle, anyone can operate the handle to control fluid flow. In particular, if this kind of valve is used in dangerous equipment, even a small mistake in the operation of the valve can cause massive damage to property and endanger human lives.
Accordingly, when valves are used in important industrial facilities, safety devices and careful management are additionally required, thereby increasing costs.